It's expensive. I paid $52.05 at my neighborhood Carquest store for a tiny 15ml bottle.
I used about one third of it treating every fuse and relay plug-in terminal in the fuse/relay box under the hood, plus all fuses and relays under the back seat.
The result? Now the one-touch open/close feature of the sunroof and driver's window work reliably instead of intermittently. The windows move up and down faster. The instrument lamps are much brighter. The turn signal flashes about twice as fast. The headlights were very bright before, but now, especially the high beams are even brighter.
It took me about two hours to do the job, and I'm sure glad I spent the fifty bucks and invested the time!
Warren '89 535i 5 spd